MOCVD GROWTH AND ULTRAFAST PHOTOLUMINESCENCE IN GAAS AND INAS FREESTANDING QUANTUM WHISKERS - A REVIEW

Nanometer size quantum whiskers of InAs and GaAs have been fabricated by low-pressure MOCVD. Time-integrated and time-resolved photoluminesc ence of GaAs wires of diameters 200, 100, 70, and 50 nm have been stud ied. The temperature dependence of PL peak energy was found to follow the same variation as the bandgap of GaAs, and Varshni's theory has be en used to explain the temperature dependence. The main channel of rad iative recombination was found to be due to free excitons. The nonunif ormity in diameter and lattice phonon interactions were considered to understand the origin of the linewidth. From the rime-resolved PL the surface recombination lifetimes were measured directly. Surface recomb ination velocities were evaluated and were correlated to wire diameter . The quantum-size-dependent spatial part of the electronic wave funct ion was thought to be responsible for the variation of surface recombi nation velocity with diameter. Surface treatment with sulphur reduced the surface depletion layer, as evidenced from the time-resolved and t ime-integrated spectra. The carrier lifetime was in picosecond lime sc ales at 7 K and increased with temperature, thus confirming the quantu m confinement effects. The polarization experiments revealed the one-d imensional nature of quantum whiskers. (C) 1994 John Wiley and sons, I nc.